Percutaneous transluminal coronary angioplasty (PTCA) is used to reduce arterial build-up of cholesterol fats or atherosclerotic plaque. According to this procedure, a blockage in a coronary artery can be reduced by positioning a balloon dilatation catheter across the blockage and inflating the balloon, which causes stretching of the artery and pressing of the lesion into the artery wall to re-establish acceptable blood flow through the artery. A guide wire is first inserted into the body and advanced through the desired coronary artery to reach a stenosis. Once the guide wire is positioned beyond the stenosis, the catheter is then slid over the guide wire so that placement of the balloon spans the stenosis and the balloon is then inflated.
Generally, guide wires have a solid core wire surrounded by one or more coil springs. The tip of the guide wire is usually shapable to allow the physician to bend the guide wire tip before insertion into the artery. The ease or difficulty of using the guide wire through the artery depends on several characteristics, such as steerability and tracking. A guide wire with superior steerability and tracking is easier to direct through a tortuous path to the stenosis. During the procedure, the guide wire is tracked by using an x-ray machine. To view the guide wire using the x-ray machine, a portion of the guide wire must be formed from a radiopaque material.
There are various ways to construct a guide wire for radiopacity. The most common way is to use spring coils mounted on the distal end of the guide wire that are radiopaque. There have been a number of patents directed to different constructions of guide wires including U.S. Pat. No. 4,757,827 to Buchbinder et al, U.S. Pat. No. 5,345,945 to Hodgson et al, U.S. Pat. No. 4,538,622 to Samson et al, U.S. Pat. No. Re. 34,695 to Mar et al and U.S. Pat. No. 5,353,808 to Viera.
One of the problems often encountered is that the guide wire has too long of a radiopaque section, making it very bright and blood flow difficult to see under x-ray. Some guide wires use multiple spring coils of different radiopacity. The problem with current multiple spring coil designs is at the joint between the coils. This same joint between the coils is also where the coils are joined to the core wire. This creates a non-flexible section on the wire in an area where the wire should have a smooth transition (See U.S. Pat. No. 5,345,945 and U.S. Pat. No. 5,353,808). What is needed is a guide wire that provides improved flexibility and a desirable amount of radiopaqueness.